Peel yams and cut into 1/2-inch slices, discarding the thin ends. Overlap slices and arrange in parallel rows in a shallow 3 quart casserole, or a 9x13 inch baking dish. Combine the sugar, cornstarch, and salt in a small pan. Gradually stir in orange juice until well blended. Bring mixture to a boil over high heat and cook, stirring for 1 minute, or until sauce is thick and clear. Remove from heat and stir in the butter and orange peel until butter melts. Pour orange sauce over the yams. Cover dish with foil (refrigerate if made ahead). To bake, place foil-covered casserole in a 400° oven for 45 minutes. Brush sauce thoroughly over tops of yams. Continue baking, uncovered, brushing with sauce several times, until yams are tender when pierced with a fork and tops are well glazed, about 15 minutes longer. Garnish with orange slices before serving. Makes 14 - 16 servings. My favorite Thanksgiving dish. Note: You can assemble the fresh yams in their orange sauce ahead of time, then put them in to bake about 1 hour before you plan to serve.